This invention pertains to jumper cables utilized to permit one vehicle with a strong battery to provide electrical energy to the weakened battery of a second vehicle. Jumper or booster cables have long been used to permit one vehicle to start another when one of the vehicles has a battery which has lost its charge. This activity is quite dangerous because it invites the possibility that the batteries themselves will explode. If the positive terminals of the two batteries and the negative terminals of the two batteries are not correspondingly interconnected, considerable damage can result to both the batteries and the jumper cables. Furthermore, the sparks which can result through connecting the conventional clamps of existing battery cables can ignite fumes in the vicinity of the batteries to cause fire and/or explosions. This is particularly true when jumper cables are connected to the batteries in boats where gaseous fumes often collect in the confined space around the battery and the boat engines.